Cationic lipid-like compounds are commonly used in vitro and in vivo to deliver DNA to cells for the purposes of expressing exogenous genes. A number of clinical trials have indicated the promise of these agents for gene therapy, however lipid-based delivery remains less effective than the alternative viral vectors. Nevertheless, vast improvements have been made over the initial formulations and lipid-like agents have an important safety advantage over modified viruses. Avanti Lipids has been marketing an unusual category of cationic lipoids that are based on the natural lipid phosphatidylcholine and which, in vitro exhibit low cell toxicity. Through a simple chemical modification, the phosphatidyl cholines are converted to cationic compounds that form complexes with DNA and are effective transfection agents. These compounds, originally developed at Northwestern University, have recently been found to give very strong synergy in mixtures; for example, a mixture of 2 such compounds is much more effective than either compound separately. Furthermore, the optimal composition depends on conditions and cells. These findings point to an entirely new approach for enhancing gene (and probably drug) delivery, suggesting that the hydrophobic portions of these molecules maybe critical for the efficacy these cationic lipid-like agents. The aim of this proposal is to survey a variety of cationic phosphatidylcholines that have unusual hydrophobic moieties that would be difficult or impossible to synthesize in any other cationic lipoid class. The lipids will be synthesized by Avanti and tested for transfection activity and characterized with respect to relevant physical properties at Northwestern. Immediate commercialization is anticipated for compounds or mixtures with 50X higher activity than current compounds, although the expectation is that compounds with even higher activity will be discovered. All proposed methods have been previously published.